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Identification and Characterization of a Novel Tobamovirus from Tropical Soda Apple in Florida

Foliar symptoms suggestive of virus infection were recently observed on the noxious weed tropical soda apple (Solanum viarum) in Florida. An agent was mechanically transmitted to Nicotiana benthamiana, and virions were isolated from systemically infected leaves. Rod-shaped particles ~300 nm in length were observed in the partially purified preparations by electron microscopy. The host range determined by mechanical inoculation with purified virions included all tested plants in the Solanaceae (16 species including the important vegetable crops, pepper and tomato) and Chenopodiaceae (2 species) but excluded all tested plants in the Ama-ranthaceae, Apocynaceae, Brassicaceae, Caryophyllaceae, Cucurbitaceae, Fabaceae, Lamiaceae, Malvaceae, and Tropaeolaceae, including several common virus indicator hosts. Comparisons of the coat and movement protein nucleotide and deduced amino acid sequences of this putative tobamovirus with recognized members of this genus, indicate that it is a novel tobamovirus that shares the highest level of sequence identity with Pepper mild mottle virus followed by other members of the Solanaceae-infecting subgroup of tobamoviruses. The virus, for which the name Tropical soda apple mosaic virus (TSAMV) is proposed, was found to be widespread in tropical soda apple in peninsular Florida during an initial survey. TSAMV contamination of seed from infected tropical soda apple plants was found, suggesting that seed transmission may be important for TSAMV dissemination and epidemiology.